Synthesis, Structures, Magnetic and Luminescent Properties of a Series of Iron(II) and Zinc(II) Coordination Frameworks with Versatile 4-Substitued 1, 2,4-Triazole Ligands

Abstract

Three multi-dentate 1, 2,4-triazole derivative ligands containing different 4-substituted groups, namely N-1, 2,4-triazol-4-yl(pyridin-3-yl)methylenimine (L1), N-1, 2,4-triazol- 4-yl(pyridin-4-yl)methylenimine (L2), and 4-(2-pyridine)-1, 2,4-triazole (L3) were used to isolate five iron(II) and zinc(II) coordination frameworks, [Zn(μ2-L1)Cl2] (1), [Zn(μ2-L2)Br2] (2), [Fe(L1)2(NCS)2(H2O)2] (3), [Fe(L3)2(dca)2(H2O)2] (4), and [Fe(L3)2(μ2-dca)] (5) (dca = dicyanamide anion). When different zinc(II) salts were used to react with L1 and L2 under solvothermal conditions, two one-dimensional (1D) zinc(II) coordination frameworks 1 and 2 containing four-coordinate central zinc(II) atoms were isolated. 1 is a 3D achiral supra-molecular framework, whereas 2 is a 3D chiral supra-molecular framework containing helical chains on a 21 axis. 3 is a mono-nuclear iron(II) coordination framework containing six-coordinate central FeII atoms. When L3 was employed, mono-nuclear iron(II) framework 4 and 1D iron(II) chain 5 could be isolated when different amounts of Nadca were introduced into the reaction system. Variable-temperature magnetic susceptibility data of 3-5 were recorded in the 2-300 K temperature range indicating weak anti-ferromagnetic interactions. The solid-state luminescent properties of coordination polymers 1 and 2 were also investigated at room temperature.